This method sends a data buffer to a resource. The data buffer is sent asynchronously using thread resources that are automatically allocated from the thread pool. The data is not encoded. To receive notification when the data upload completes, add an event handler to the UploadDataCompleted event.

This method does not block the calling thread while the data is being sent. To send data and block while waiting for the server's response, use one of the UploadData methods.

Asynchronous operations that have not completed can be canceled using the CancelAsync method.

If the BaseAddress property is not an empty string (""), and address does not contain an absolute URI, address must be a relative URI that is combined with BaseAddress to form the absolute URI of the requested data. If the QueryString property is not an empty string, it is appended to address.